1. Field of the Invention
The present invention relates to cable bolts and, in particular, cable bolts that are installed in mine roof boreholes.
2. Description of Related Art
Cable bolts are used in the mining industry for their ease of handling and installation. Cable bolts are substantially easier to fit into a borehole than the elongated rods of conventional rod bolt systems. Regardless of the height limitations in a mine, cable bolts may be adapted to boreholes of any length due to their flexibility. The strength capacity of cables typically exceeds that of conventional rod bolts and, therefore, cable is the preferred reinforcement for certain roof conditions. Cable bolts are typically installed by placing a resin cartridge, including catalyst and adhesive material, into the blind end of a borehole, inserting the cable bolt into the borehole so that the upper end of the cable bolt rips open the resin cartridge and the resin flows in the annulus between the borehole and the cable bolt, rotating the cable bolt to mix the resin catalyst and adhesive, and allowing the resin to set about the cable bolt. In such cable bolts, the resin is typically set at an upper portion of the cable bolt at the blind end of the borehole. In certain installations of mine roof bolts, fully grouting the entire length of the bolt that is received within the borehole may be desirable so as to provide extended corrosion protection and/or enhanced anchorage in the surrounding rock strata.
Cable bolts tend to be longer in length than standard fully grouted rebar bolts, which allow cable bolts to reach higher layers of strata that may contain large amounts of water in the cracks and fissures of the rock strata. The water can flow out of a borehole at several gallons per minute, which may cause poor working conditions and slow mine production.